Hydrogen, sulphide

Sulphides.—Hydrogen Sulphide. The far-i.r. rotational absorption spectra of H28, 8O2, and NO2 have been recorded between 10 and 40 cm at a resolution of 

Bali and K. C. Malhotra, J. butrg. Nuclear Chem., i976, 38, 411. 

lippert, and E. Erdos, ColL Czech. Chem. Comm., 1976, 41, 675. 

Hydrogen sulphide is poisonous Perform all experiments with it in a fume cupboard. Immediately take a student poisoned by hydrogen sulphide from the laboratory into the fresh air or let him or her inhale pure oxygen. 

Preparation. Put 1-2 g of iron sulphide into a test tube and pour in 5-8 ml of a 20% hydrochloric acid solution. Close the tube with a stopper provided with a drawn out gas-discharge tube (see Fig. 42). 

Properties. 1. What odour does the evolving gas have Light the hydrogen sulphide with a burning splinter, hold a wet piece of litmus paper over the flame, and watch how its colour changes. Write the equation of the reaction. 

Introduce the cold lid of a crucible into the hydrogen sulphide flame. What appears on the surface of the lid Write the equation of the reaction. 

Pour bromine water, chlorine water, and acidified solutions of potassium permanganate and dichromate into separate test tubes. Pass a stream of hydrogen sulphide through all the tubes. What happens Write the equation of the reactions. What property of hydrogen sulphide is indicated by the occurring phenomena  

Hydrogen Sulphide.—Ion-molecule reaetions in methanol and H2S have been studied using a photoionization quadrupole mass spectrometer the proton affinity of H2S was determined. The sulphur emission and K absorption spectra from gaseous H2S have been measured. The spectrum comprises four peaks and the absorption spectrum three peaks that are of decreasing energy with increasing photon energy. 

Hydrogen sulphide has been shown to react with bromide ions in a eutectic melt of lithium and potassium bromides according to the equation  

The reaction follows closely that observed for chlorine with H2S, the only difference being that the equilibrium constants and reaction rates are lower in the case of Br . A study of the kinetics of the reaction between H2S and Pb ions in a eutectic melt of LiCl and KCl has allowed the following reaction scheme to be suggested  

The oxidation of H2S (by O2) over microporous carbons has been studied. The predominant reaction  

Hydrogen Sulphide.— The differences in the proton affinities of H28 and HgO have been measured in a photoionization mass spectrometer by studying the equilibrium  

Mixtures of HgS and HgO are photolysed at 10.63 eV in the source of the mass spectrometer. H2S+, which is the only ion produced, reacts with H2S to give H3S+. This ion reacts with H2O to produce H3O+, which further hydrates to H(H20) . The proton affinity of H2S was found to be some 3 kcal mol greater than that of H2O. The electron-impact-induced ionization and dissociation of H2O and H28 have been studied using a quadrupole mass spectrometer, and a comparison has been made with the corresponding photoionization and photoelectron spectra. I.r. studies on the adsorption 

Morrison and J. C. Trheger, Internat. J. Mass Spectrometry Ion Phys., 1973,11, 

The reaction between hydrogen atoms and H2S, with and without added NO, has been studied by following the H atom, S atom, and SH radical concentrations with time, by e.s.r. techniques. The results of the study may be fully explained by the mechanism  

Hydrogen sulphide is produced by obligate anaerobic bacteria if there are abundant sulphate and organic substrates at redox potentials below zero. 

Sulphide production has been observed in the rhizosphere and spermosphere 24 21 29 

Eeggiatoa on rice roots oxidize hydrogen sulphide extracellularly to sulphur 

In the presence of excess Fe, the formation of insoluble ferrous sulphide 

The reaction of hydrogen sulphide with solutions of calcium, strontium, or barium in liquid ammonia has been shown205 to give precipitates of the 

Ab initio MO calculations for the potential curves of H2S+ and HzO+ have been carried out208 in order to obtain a theoretical description of the electronic structure and geometry of these systems. The results are in satisfactory agreement with experiment, and show that both radicals are very similar, both in geometry and in electronic structure. 

Blaise, A. Genty, and J. Bardolle, Bull. Soc. chim. France, 1974, 1229. 

Most of the known chemistry in liquid hydrazine covers protolytic reactions, and may be referred to the self-ionization in the pure liquid state  

Hydrazinium compounds such as hydrazinium perchlorate act as acids in this medium. Apart from the N2Hs+-ion the existence of N2He has been shown in compounds like hydrazinium difluoride N2H6F2 . 

Since the proton affinity of hydrazine is similar to that of ammonia, acid-base reactions are similar to those in this solvent system. Many compounds are known to act as moderately strong acids, but only a few substances (notably the hydra-zides of the alkali metals) behave as bases. NaN2H3 may be obtained by drop wise addition of hydrazine to a suspension of finely divided sodium in dry ether. Electrolysis in liquid hydrazine gives nitrogen at the anode and hydrogen at the cathode . 

Hydrogen sulphide is a poor ionizing solvent of low donor properties. It is only very weakly hydrogen bonded in the liquid state and has a low dielectric constant the donor properties are considerably lower than those of water and indeed acceptor properties are also apparent. 

Barlot, j., and S. Marsaule Compt. Rend. Acad. Sci. Paris 228, 1497 (1949). 

A chain reaction involving S and H atoms and SH radicals may be operative. The authors discuss a bimolecular step 2 H2S - 2H2+S2 but it is hard to see how this one-reaction mechanism would take place. 

Shock-tube experiments on the decomposition of hydrogen sulphide have been performed but were unsuccessful because traces of oxygen and other oxidizers could not be removed from the reactant24. No data are available on the homogeneous decomposition of hydrogen polysulphides, nor have the kinetics of pyrolysis of selenium and tellurium hydrides been studied. 

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CfiHsNjOs. Red needles m.p. 168-169°C. Soluble in dilute acids and alkalis. Prepared by reduction of picric acid with sodium hydrogen sulphide, ft is used for the preparation of azodyes, which can be after-chromed by treatment with metallic salts owing to the presence of a hydroxyl group ortho to the amino-group. 

Corrosion service Carbon dioxide (CO2) or hydrogen sulphide (H2S) in formation tluids will cause rapid corrosion of standard carbon steel and special steel may be required... 

Composition - which describes the proportion of hydrocarbon components (C, - Cj+) (which determine the fluid properties), and how many non-hydrocarbon substances (e.g. nitrogen, carbon dioxide and hydrogen sulphide) are present. 

To prepare gas for evacuation it is necessary to separate the gas and liquid phases and extract or inhibit any components in the gas which are likely to cause pipeline corrosion or blockage. Components which can cause difficulties are water vapour (corrosion, hydrates), heavy hydrocarbons (2-phase flow or wax deposition in pipelines), and contaminants such as carbon dioxide (corrosion) and hydrogen sulphide (corrosion, toxicity). In the case of associated gas, if there is no gas market, gas may have to be flared or re-injected. If significant volumes of associated gas are available it may be worthwhile to extract natural gas liquids (NGLs) before flaring or reinjection. Gas may also have to be treated for gas lifting or for use as a fuel. 

If produced gas contains water vapour it may have to be dried (dehydrated). Water condensation in the process facilities can lead to hydrate formation and may cause corrosion (pipelines are particularly vulnerable) in the presence of carbon dioxide and hydrogen sulphide. Hydrates are formed by physical bonding between water and the lighter components in natural gas. They can plug pipes and process equipment. Charts such as the one below are available to predict when hydrate formation may become a problem. 

The most common contaminants in produced gas are carbon dioxide (COj) and hydrogen sulphide (HjS). Both can combine with free water to cause corrosion and H2S is extremely toxic even in very small amounts (less than 0.01% volume can be fatal if inhaled). Because of the equipment required, extraction is performed onshore whenever possible, and providing gas is dehydrated, most pipeline corrosion problems can be avoided. However, if third party pipelines are used it may be necessary to perform some extraction on site prior to evacuation to meet pipeline owner specifications. Extraction of CO2 and H2S is normally performed by absorption in contact towers like those used for dehydration, though other solvents are used instead of glycol. 

In presence of hydrochloric acid, tin(II) in aqueous solution (1) is precipitated by hydrogen sulphide as brown SnS, and (2) will reduce mercury(II) chloride first to mercury(I) chloride (white precipitate) and then to metallic mercury. 

Tin(IV) in aqueous acid gives a yellow precipitate with hydrogen sulphide, and no reaction with mercury(II) chloride. 

Arsenates(V) are more powerful oxidising agents than phos-phates(V) and will oxidise sulphite to sulphate, hydrogen sulphide (slowly) to sulphur and, depending on the conditions, iodide to iodine. 

When hydrogen sulphide is bubbled into an acidic solution of an antimony or a bismuth salt an orange precipitate, SbjSs, or a brown precipitate, BijS, is obtained. Bismuth(III) sulphide, unlike antimony(IIl) sulphide, is insoluble in lithium hydroxide. 

Large quantities of sulphur are recovered from petroleum and natural gas. Naturally occurring hydrogen sulphide, HjS, and that produced in the cracking and catalytic hydrogenation of petroleum is first removed by absorption and the regenerated gas is converted to sulphur by partial combustion with air, the overall reaction being,... 

In addition to the hydrides of formula HjX, oxygen forms the hydride H2O2, hydrogen peroxide, and sulphur forms a whole series of hydrides called sulphanes. These are yellow liquids which are thermodynamically unstable with respect to hydrogen sulphide and sulphur. 

Lead(II) sulphide is oxidised to lead(II) sulphate this reaction has been used in the restoration of old pictures where the white lead pigment has become blackened by conversion to lead sulphide due to hydrogen sulphide in urban air ... 

Sulphur can be reduced directly to hydrogen sulphide by passing hydrogen through molten sulphur the reversible reaction H2 -I-S H2S occurs. In the laboratory the gas is most conveniently prepared by the action of an acid on a metal sulphide, iron(II) and dilute hydrochloric acid commonly being used ... 

The gas is washed with water to remove any hydrogen chloride. Since iron(II) sulphide is a non-stoichiometric compound and always contains some free iron, the hydrogen sulphide always contains some hydrogen, liberated by the action of the iron on the acid. A sample of hydrogen sulphide of better purity can be obtained if antimony(III) sulphide, (stibnite) SbjSj, is warmed with concentrated hydrochloric acid ... 

Alternatively pure hydrogen sulphide is obtained by the hydrolysis of aluminium(III) sulphide ... 

Hydrogen sulphide is a colourless gas, b.p. 213 K, with a most unpleasant odour the gas is very toxic, but the intense odour fortunately permits very minute concentrations of the gas to be detected. 

Hydrogen sulphide bums in air with a blue flame yielding sulphur dioxide, but if the air supply is limited, preferential combustion to form sulphur occurs ... 

Hydrogen sulphide is slightly soluble in water, giving an approximately 0.1 M solution under 1 atmosphere pressure it can be removed from the solution by boiling. The solution is weakly acidic and dissolves in alkalis to give sulphides and hydrogensulphides. The equilibrium constants... 

Hydrogen sulphide is a reducing agent in both add and alkaline solution as shown by the following examples ... 

Hence the orange colour of a dichromate is converted to the green colour of the hydrated chromium(III) ion, Cr ", and sulphur is precipitated when hydrogen sulphide is passed through an acid solution.)... 

Hydrogen sulphide reacts slowly with many metals (more rapidly if they are heat ) to yield the sulphide of the metal and (usually) hydrogen, for example the tarnishing of silver. 

Since most metallic sulphides are insoluble, many are precipitated when hydrogen sulphide is passed through solutions containing ions of the metals. Some are precipitated in acid, and others in alkaline... 

These two gases can readily be prepared by the action of acids on selenides and tellurides respectively, the reactions being analogous to that for the preparation of hydrogen sulphide. 

These gases have lower thermal stabilities than hydrogen sulphide as expected from their enthalpies of formation Table 10.2) and they are consequently more powerful reducing agents than hydrogen sulphide. 

Since the hydrogen-element bond energy decreases from sulphur to tellurium they are stronger acids than hydrogen sulphide in aqueous solution but are still classified as weak acids—similar change in acid strength is observed for Group Vll hydrides. 

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